Dimensional Tolerances in Construction and for Surface Accessibility

1.1.1 Measurement tools. Distance measuring devices should be capable of measuring to a precision of 1/16 in. (1 mm). Angular or slope measuring devices should be capable of measuring to a precision of 0.1 degree and elevation measuring devices should be capable of measuring to a precision of 0.01 ft (1/8 in. or 3 mm).

For measuring device accuracy, the instrument and technique for measurement should provide for an accuracy of at least one - third the required tolerance. For tolerance measurement requirements of 1/8 in (3 mm) this would mean a device capable of measuring to about 3/64 in. Because this is not realistic in construction, a tape measure with 1/16 in. divisions is a reasonable compromise for inch - pound units. For metric measure, most tapes are marked in 1 mm units, which make them ideal for determining 3 mm tolerances.

If some tolerances are set at 0.5% slope (0.2865 degrees or approximately 0.3 degrees), then the accuracy of the instrument for measuring slope should be ±0.1 degree. Digital inclinometers (SmartTool®), floor profilers, and other electronic instruments are capable of measuring to this accuracy. 0.01 ft accuracy for elevations is common in surveying and nearly all instruments, including metal tapes, can achieve this accuracy.